The present invention relates to cold starting and evaporative emission control of a spark-ignition, fuel injection internal combustion engine and has for an object the provision of a simple and effective cold start and evaporative control system for use in such engine
I. for selectively eluting from a full range fuel flowing to the engine, only the lower molecular weight constituents at cold start so as to allow quick starting of the engine without excessive amounts of unburned hydrocarbons appearing at the exhaust (cold start cycle) as well as PA1 Ii. for adsorbing evaporative emissions from the gasoline tank when the engine is not operating (vapor capture cycle), without mileage loss.
Higher molecular weight constituents adsorbed during the cold start cycle and/or light, evaporative emissions adsorbed during the vapor capture cycle of the engine are subsequently purged from the engine, by consumption interior thereof, but only after the engine has warmed and full range fuel is being utilized.
In my parent application cited above, I taught how cold starting of a spark-ignition, fuel injection internal combustion engine could be enhanced, such enhancement occurring without generating unburned hydrocarbons at the engine's exhaust. Specifically, as cold start conditions occur (cold start operating mode), just enough lower molecular weight constituents of a full-range fuel can be dynamically eluted for cold starting of the engine. The described elution system includes an adsorbent bed of adsorbent material packed within a cannister assembly. Fuel flow control from a fuel reservoir is by means of a controller circuit acting through a valve and conduit network. Initiation of the cold start cycle is straight-forward, as by means of a change in state of the ignition switch. In addition to the aforementioned cold start capabilities, my system also has the added feature of being able to adsorb evaporative emissions originating from within the gasoline tank when the engine is inoperative, such emission capture occurring not within the above-identified adsorbent bed, but within a second adsorbent bed located coextensively with, but coaxially exterior thereof. However, since the cannister assembly supporting both first and second beds had to include an internal separation wall, experience has shown that the resulting cannister assembly could be rather costly and time-consuming to fabricate.
In accordance with the present invention, rather than requiring complex, double-wall construction, my cannister assembly now requires only a single adsorbent bed for performing the aforementioned dual functions. Thus in one embodiment, the cannister assembly uses only a single unitary sidewall to form the annular support space at its interior. Into the unitary space adsorbent materials are packed capable of interchangeably functioning as either an elution or emission capture adsorbent bed. Inasmuch as the two separate functions are interchangeable, it is essential that the adsorbent material (constituting the aforementioned adsorbent bed) be properly classified for these functions, viz, either polar or nonpolar or a combination thereof.
In many applications, a composite mixture of polar and nonpolar adsorbent materials is preferred. The range of the mix ratio, by volume, can be varied depending upon the nature of conditions encountered in the field. That is, in geographically humid zones of the world, such as found in the sourthern part of the United States, there may be a requirement for the use of greater amounts, by volume, of the nonpolar adsorbent constituent material for the purpose of increasing capture area of the cannister assembly. Results: increased probability of total adsorption of vapor emissions generated within the fuel system. Similarly, in colder climatic zones where start conditions are more severe, there may be some advantage to provide greater amounts of polar adsorbent material during the cold start cycle of the engine. The key requirement in both cases, of course, remains to provide polar and nonpolar adsorbent constituent materials in a combination that assures both efficient elution and capture modes of operation within the cannister assembly of the present invention.
Construction of the improved cannister assembly in accordance with present invention can vary. For example, in one embodiment a simple cylinder can be plugged at both ends with solid, annular pole pieces. Entry and egress of the engine fuel is by means of radially extending fittings connected through the valve and conduit network to the fuel reservoir.
All operating cycles are automatically controlled through a fuel injection control circuit similar to one I previously proposed and described in the above-identified parent application. The fuel injection control circuit, in turn, acts in conjunction with the valve and conduit network to allow (or prevent) fluid flow, depending on the operating cycle.
In more detail, during the cold start cycle, the valve and conduit network is arranged to allow free passage of the full-range fuel into contact with the adsorbent bed say through a radial inlet fitting and thence by percolation thereover. Selective retardation of the higher molecular weight compounds, vis-a-vis the lower components then occurs. Thereafter, the latter constituents pass from a second radial outlet fitting to each of a series of electromagnetic injectors in a preselected time sequence, as well as in a preselected air-fuel ratio. Results: the engine starts even under the most severe climatic conditions. Since the starting cycle is usually quite short, say from 1 to 15 seconds, the residence time for the high molecular weight compounds within the elution zone is preferably 1 to 2 orders longer say from 1 to 3 minutes. Thus, the heavier compounds remain selectively adsorbed with the adsorbent bed during starting of the engine. Thereafter, the adsorbent bed is disconnected from direct fuel flow by the controller. The full-range fuel from the reservoir, then is forced to flow in a direct path to the electromagnetic injectors. As the full-range fuel is used and the cannister is disabled, it should be noted that the latter undergoes depressurization. Result: as the engine warms and hot air is passed adjacent to the cannister, adsorbed materials (adsorbents) within the adsorbent bed, are easily purged from the system.
In still more detail, during the inoperative state of the engine (the vapor capture cycle), the same adsorbent bed interior of the cannister assembly is automatically placed in fluid contact with the gasoline tank through operation of the same controller and network system. Thus, the evaporative emissions are free to pass into and be captured by the aforementioned adsorbent bed. Since studies indicate that up to 15% by volume of the total vapors admitted into the atmosphere during inoperativeness of I.C. engines are traceable to evaporative emissions originating from fuel sources of such engines, the present invention provides a useful solution to a serious environmental problem.
Since the function of the associated valve and conduit network and the fuel injection control conduit is to place the adsorbent bed of the cannister assembly in fluid flow relationship with relevant elements of the fuel system as required, it is apparent that after the engine has been started and adequately warmed, adsorbates within the adsorbent bed (due to the elution and capture cycles) can be automatically purged from the cannister; gases (either full or partial engine air or manifold exhaust gases) can be passed adjacent to the cannister assembly, as required.
Although the prior art has suggested both polar and nonpolar adsorbent materials for use in enhancing operation of I.C. fuel systems, there has been no suggestion of using commonly housed adsorbent materials in an unitary elution system to serve two functions: (i) selectively eluting from a full-range gasoline, only light, low molecular weight components thereof, to assure a smooth pollution-free start of a spark-ignition fuel injection internal combustion engine while alternatively (ii) providing for capture of evaporative emission originating from the associated fuel system when the engine is in an inoperative state.
Further objects, features and attributes of the present invention will become apparent from a detailed description of several embodiments thereof to be taken in conjunction with the following drawings in which: